Diabetic retinopathy is a cause of blindness in diabetic patients and so it is important to be able to screen patients for evidence of this disease. Such screening typically involves examination of digital color fundus images to identify different symptoms related to the disease: microaneurysms, hemorrhages, vascular abnormalities, among others. In particular, the number, density and locations of microaneurysms are important factors to quantify the progression of diabetic retinopathy in its early stages.